CORRELATION OF ULTRAVIOLET AND RADIO FLUX IN 3 ACTIVE GALACTIC NUCLEI

We report the results of a search for correlations between the time-va riable ultraviolet (UV) and the radio flux in three AGNs, viz., 3C 273 , 3C 120, and PKS 2155-304. Data from 1984 to present were used. UV da ta from the short-wave IUE camera were downloaded from the IUE Regiona l Data Analysis Facility and the National Space Science Data Center at NASA/GSFC. Radio flux at 4.8, 8.0, and 14.5 GHz were obtained from th e University of Michigan Radio Astronomy Observatory by Aller et al. T he UV flux at 1550 Angstrom and UV spectral index were obtained by fit ting power law to the short-wave continuum of each IUE spectrum. Cross -correlation and discrete-correlation functions were computed for the UV and radio fluxes over a common time interval of more than 5 yr. Cro ss-correlation analysis was also carried out between spectral indices in the UV and radio bands for the three objects. Significant correlati ons were found at one or more time lags for each of the three objects. The possibility that cross correlation analysis can yield delusive re sults is discussed.